Create todo.py

todo.py

@@ -0,0 +1,208 @@
+import json
+import os
+
+# Define the file where tasks will be stored.
+DATA_FILE = "tasks.json"
+
+def load_tasks():
+    """
+    Loads tasks from the DATA_FILE.
+
+    If the file does not exist, an empty list is returned.
+    Handles potential JSON decoding errors or OS-related file errors.
+
+    Returns:
+        list: A list of dictionaries, where each dictionary represents a task.
+              Returns an empty list if the file is not found or corrupted.
+    """
+    # Check if the data file exists. If not, there are no tasks to load yet.
+    if not os.path.exists(DATA_FILE):
+        return []
+    try:
+        # Open the file in read mode with UTF-8 encoding for broader character support.
+        with open(DATA_FILE, "r", encoding="utf-8") as f:
+            # Load the JSON data from the file.
+            return json.load(f)
+    except (json.JSONDecodeError, OSError) as e:
+        # Catch errors if the JSON is malformed or if there's an OS-related error
+        # (e.g., permission denied, disk error during read).
+        print(f"Error loading tasks: {e}. Starting with an empty task list.")
+        return []
+
+def save_tasks(tasks):
+    """
+    Saves the current list of tasks to the DATA_FILE.
+
+    Handles potential OS-related file errors during saving.
+
+    Args:
+        tasks (list): The list of task dictionaries to be saved.
+    """
+    try:
+        # Open the file in write mode with UTF-8 encoding.
+        # `ensure_ascii=False` allows non-ASCII characters (like emojis) to be saved directly.
+        # `indent=2` formats the JSON for better readability.
+        with open(DATA_FILE, "w", encoding="utf-8") as f:
+            json.dump(tasks, f, ensure_ascii=False, indent=2)
+    except OSError as e:
+        # Catch errors if there's an OS-related error during write (e.g., permission denied, disk full).
+        print(f"Error saving tasks: {e}. Your changes might not have been saved.")
+
+def list_tasks(tasks):
+    """
+    Prints all tasks to the console, showing their status and index.
+
+    Args:
+        tasks (list): The list of task dictionaries to display.
+    """
+    if not tasks:
+        print("No tasks to display.")
+        return
+
+    print("\n--- Your To-Do List ---")
+    for i, t in enumerate(tasks, 1):
+        # Determine the status symbol based on the 'done' flag.
+        status = "✔" if t["done"] else "✗"
+        print(f"{i}. [{status}] {t['title']}")
+    print("-----------------------\n")
+
+def add_task(tasks, title):
+    """
+    Adds a new task to the list.
+
+    Args:
+        tasks (list): The current list of task dictionaries.
+        title (str): The title of the new task.
+    """
+    title = title.strip() # Remove leading/trailing whitespace
+    if not title:
+        print("Error: Task title cannot be empty.")
+        return
+
+    # Create a new task dictionary with a default 'done' status of False.
+    tasks.append({"title": title, "done": False})
+    save_tasks(tasks) # Save the updated list to file.
+    print(f"Task '{title}' added successfully.")
+
+def toggle_task(tasks, index_str):
+    """
+    Toggles the 'done' status of a task at the specified index.
+
+    Args:
+        tasks (list): The current list of task dictionaries.
+        index_str (str): The string representation of the 1-based index of the task.
+    """
+    try:
+        index = int(index_str)
+    except ValueError:
+        print(f"Error: Invalid task number '{index_str}'. Please enter a valid integer.")
+        return
+
+    # Adjust index to be 0-based for list access.
+    # Validate the index to ensure it's within the bounds of the task list.
+    if index < 1 or index > len(tasks):
+        print(f"Error: Task number {index} is out of range. Please choose a number between 1 and {len(tasks) if tasks else 0}.")
+        return
+
+    # Toggle the 'done' status.
+    tasks[index - 1]["done"] = not tasks[index - 1]["done"]
+    save_tasks(tasks) # Save the updated list.
+    status_msg = "completed" if tasks[index - 1]["done"] else "marked as not completed"
+    print(f"Task {index} '{tasks[index-1]['title']}' {status_msg}.")
+
+def delete_task(tasks, index_str):
+    """
+    Deletes a task from the list at the specified index.
+
+    Args:
+        tasks (list): The current list of task dictionaries.
+        index_str (str): The string representation of the 1-based index of the task.
+    """
+    try:
+        index = int(index_str)
+    except ValueError:
+        print(f"Error: Invalid task number '{index_str}'. Please enter a valid integer.")
+        return
+
+    # Adjust index to be 0-based for list access.
+    # Validate the index.
+    if index < 1 or index > len(tasks):
+        print(f"Error: Task number {index} is out of range. Please choose a number between 1 and {len(tasks) if tasks else 0}.")
+        return
+
+    # Remove the task from the list and store its title for confirmation message.
+    removed_task_title = tasks.pop(index - 1)["title"]
+    save_tasks(tasks) # Save the updated list.
+    print(f"Task {index} '{removed_task_title}' deleted successfully.")
+
+def help_menu():
+    """
+    Displays the help menu with available commands.
+    """
+    print("\n--- Commands ---")
+    print("  list                : Show all tasks.")
+    print("  add <title>         : Add a new task with the given title.")
+    print("  done <num>          : Toggle the completion status of task <num>.")
+    print("  del <num>           : Delete task <num>.")
+    print("  help                : Show this help message.")
+    print("  quit                : Exit the application.")
+    print("----------------\n")
+
+def main():
+    """
+    The main function to run the To-Do List application.
+    It loads tasks, enters a command loop, and processes user input.
+    """
+    tasks = load_tasks() # Load tasks at the start of the application.
+    print("Welcome to the Simple To-Do List!")
+    help_menu() # Display the help menu initially.
+
+    while True:
+        try:
+            # Prompt the user for a command.
+            cmd_input = input("> ").strip()
+        except (EOFError, KeyboardInterrupt):
+            # Handle Ctrl+D (EOFError) or Ctrl+C (KeyboardInterrupt) to exit gracefully.
+            print("\nExiting To-Do List. Goodbye!")
+            break
+
+        # If the input is empty, just prompt again.
+        if not cmd_input:
+            continue
+
+        # Split the command into action and arguments.
+        parts = cmd_input.split(maxsplit=1)
+        action = parts[0].lower() # Convert action to lowercase for case-insensitive comparison.
+
+        if action == "list":
+            list_tasks(tasks)
+        elif action == "add":
+            # Check if a title was provided for the 'add' command.
+            if len(parts) < 2:
+                print("Usage: add <title> (e.g., add Buy groceries)")
+            else:
+                add_task(tasks, parts[1])
+        elif action == "done":
+            # Check if a task number was provided and if it's a digit.
+            if len(parts) < 2:
+                print("Usage: done <num> (e.g., done 1)")
+            else:
+                toggle_task(tasks, parts[1])
+        elif action == "del":
+            # Check if a task number was provided and if it's a digit.
+            if len(parts) < 2:
+                print("Usage: del <num> (e.g., del 2)")
+            else:
+                delete_task(tasks, parts[1])
+        elif action == "help":
+            help_menu()
+        elif action == "quit":
+            print("Exiting To-Do List. Goodbye!")
+            break
+        else:
+            # Inform the user about unknown commands.
+            print(f"Unknown command: '{action}'. Type 'help' to see available commands.")
+
+# Entry point for the script.
+if __name__ == "__main__":
+    main()